Dear Margaret Little and list,
RE:>> What success rate should it have on the nematode "virus"--(Authors note: Nematodes are a multicellular pest but not a virus)
See: "Biology and Management of Foliar Nematodes", by Parwinder Grewal and Ganpati B. Jagdale, THJ, Vol 32 No1, Pgs 64-66; "Control of Foliar Nematodes on Hostas", by James R. Baker and Edwin A. Shearin, THJ, Vol 30 No 1, Pgs. 78-83; and Google "sugar beets nematode resistance").
Abstract: Try Zerotol if you can't use Nemacur or Vydate, or simply let the plant increase its level of nematode resistance on its own.
I love this discussion on nematodes for several reasons; 1) It gives us an excuse to get out in the garden and see the Hostas, 2) there are several different approaches that are recommended and it's informative to see tried, and even proven, remedies, and 3) it shows that pests and diseases in plants are alive and well, and therefore that the EPA won't be able to totally obliterate pesticides until they eliminate pathogens.
I first observed nematodes in my garden in 2000. Since then, I've undertaken further study on the subject, to the point of being encouraged to determine if the Hs1(pro-1) gene is present in the Hosta genome (a nematode resistant gene that is quickly activated to promote nematode resistance in sugar beets, tobacco, arabidopsis thaliana, etc.), to be followed (hopefully) by more research.
I have seen recommendations for: 1) radical treatment methodologies (dig up the plant including surrounding soil and throw the whole mess into the trash); 2) something my grandmother used to do--poor very hot water onto the soil around the plant (or for the more scientific approach, see the reference of J. R. Baker above), 3) Potting them up (for possibly a year, so that the pot temp will reach closer to 110-120F degrees--greenhouse propagated Hosta don't seem to have nematode problems), or putting them in a bag inside the car for a few hours to achieve the same effect, and 4) treating them with chemicals (see Dr. Grewal, et. above).
Treatments 2-4 seem worth a shot prior to trashing the plant, unless you can readily find another good copy and/or you don't care about the cost, wouldn't you agree?
I have yet to treat for them, but am making plans for this fall and next spring, simply because most Hosta people don't undertand wanting your garden to be a research lab--i.e. to some, if the plant has a flaw it's a curse and who would allow such to happen? Such people must be "plant abusers"! Because the AHS convention is here in 2004, it's highly desireable to have flawless plants but otherwise, I usually don't mind moderate damage from slugs/pests or pathogens. Such give nature a chance to evolve, and me a chance to observe which plants I would recommend to others and which I would not. Or, at least to provide a caveat, as in, "H. 'Brim Cup'--it's a lovely plant but be aware that it is slug bait".
What I have observed is that nematodes are to Hosta what viruses are to Hosta--an opportunity for a plant to either enhance its immune system to ward off further infestation, or to decline or even die. Because angiosperms have evolved over some 600M+ years, some display a marvelous immune system but it takes awhile for the immunity to display itself.
What I would like to see developed is a listing of plants that appear to be foliar nematode resistant, at least on a scale of from being easily obliterated (Golden Tiara comes to mind), to highly resistant (Willam Lachman seems to take a licking and keep on ticking). Or, maybe if we observe what happens from year to year, i.e. one year a plant is infested and then the next it appears to be totally immune, we could develop a valuable database. The question is, who would do it and is it worth the time and expense? Ran Lydell recommended the same for viruses when he was in my garden years ago. In my mind, this datum is as important as listing vein pairs or coloration yet establishing the criteria on a registration form would take some effort. Which entity will fund the effort? The U.S. Government used to but it looks like we might be a little short on research cash?
While the easy thing to do is get your certified chemical applicators license and then spread nemacur all over the garden (or simply hire a professional to do the same, for about $500), I wonder if by applying chemicals we are defeating the plants natural ability to resist the infestation because we don't give the Hs1(pro-1) (nematode resistance promoter gene) time to activate? This may be an explanation for why one year Willian Lachman appears to be nematode bait and the next it is clear? Further investigation is warranted.
Scientists who study such things have observed that, at least for sugar beets, the level of Hs1(pro-1) is four times higher after nematode infestation than before. For perennials that have such a gene in their genome, this is certainly good news. The question remains as to which Hosta have this promoter gene, if any.
Until then, we've heard things from Dr. Grenwald about Zerotol and nematode treatment. Why not give Zerotol a try if you can't get Nemacur (available from Bayer Agricultural products but a restricted use chemical). Or, let the Hs1 or Hs2 nematode resistance gene do its thing... Good luck!
P.S. Maybe, if we're lucky, we can get Plant Delights' on-staff Nematologist to weigh-in on this topic.
Des Moines, IA -- Zone 5a
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